I am working on wpf mvvm pattern. I have different user controls. Based on the checkbox selection, I want them to be loaded in the main screen (that is also a user control). I have one HomeViewModel class which I have been using to bind the user controls of my project. Can you help me with a suitable way?
You should have different ViewModels for each kinds of UserControl.
Create different DataTemplates for each ViewModel Types
Put a ContentControl with binding a property of HomeViewModel -
Value of property will be an instance of ViewModel ( UserControl's) and is set by toggling CheckBoxes.
Related
I'm working on a project that utilizes WPF, using the Prism library and Unity Container.
I have a mainwindow, which contains a mainviewmodel control which in turn is populated by a collection of user controls.
My goal is to set keyboard focus to the mainviewmodel where I have an EventTrigger InvokeCommandAction which reacts to keyeventsargs...
Currently the only way the command is fired if I use a textbox within the control (or child controls). My goal is to have the mainviewmodel control or grid get and preserve keyboard focus.
Any tips would be appreciated!
//Nathan
Either not understanding your question correctly or you should review the basic concepts of MVVM in a WPF implementation.
The View is the WPF controls.
WPF Window/UserControl files contain WPF markup which is the View.
Controls in a view leverage DataBindings to the DataContext property of either the control itself or the parent containing control (which it will inherit).
DataContext property is set to an instance of an object that is the ViewModel. It contains properties to hold values and commands to execute actions.
So conceptually there is no "mainviewmodel control", there is a MainView which contains controls and may in this case have its DataContext property set to an instance o MainViewModel. (hence my confusion)
Finally, while it is possible and some might even recommend writing UI rules/logic in a view model I haven't found much benefit in it.
You are much better off putting UI logic in the XAML or in the MinView code behind. You can still access the MainViewModel in the code behind by casting the MainView.DataContext property as a MainViewModel.
So for example:
MainView.KeyDown event can be wired up to call MainViewModel.CommandX.Execute();
On my view I have different Controls. Mostly Buttons, TextBoxes and ComboBoxes. The Buttons are enabled/disabled via CommandBinding (ICommand), but the other controls must be enabled/disabled "manually". I can think of many ways to achieve this:
Adding a bool-Property to the ViewModel is one way and using DataTriggers is an other. (Or maybe I could bind the Property directly and use a IValueConverter.)
Is there a particular solution in MVVM that I am leaving out or missing?
Yes, you can bind a public boolean property on your view model to the IsEnabled property of the control. There is no need for a value converter.
i have a problem with WPF MVVM, i have one usercontrl loaded inside my main view.. And at my main view i have a status bar and one textbox. I want to change the text by clicking at button from usercontrol, how can i do that? I tried a lot os things here like raisedpropertiechange and nothing happens.
I have one ViewModel from MainModel and a lots of UserControls with theirs viewmodels. Each usercontrl viewmodel will have one button with need to be fired and change the text from parent Model.
Im not sure if im clear about this.
Regards
I would provide a command in the BaseClass of the UserControl viewmodel, which changes the text in the parent viewmodel of the UserControls viewmodel. The Buttons of the UserControl can bind to this command. And the title of the main view is bound to the text property.
Keep the views and controls as decoupled and 'stupid' as possible.
Then you only have to provide a reference of the main viewmodel in the other viewmodels.
In my WPF application, I have a usercontrol library. In this library, I have a listview control along with textbox and button controls.
I have placed this usercontrol in a WPF window form. How can I retrieve the listviewitems of my usercontrol in this WPF window form?
You ask a very general question. There are dozens of ways to do that, depends on your needs. For example: when you place you UserControl within the Window - you should name it (e.g. . Then, within the UserControl, you can have a public function, or a public getter, which will return the items (it is the 'Items' property of the ListView).
Another way is binding. If you have a ViewModel, or any other class as the DataContext, you can bind the ItemsSource of the ListView to a collection on your ViewModel. Unless you change the DataContext of the UserControl - it will have the same DataContext as the main Window.
I have two ViewModels that present the same Model to different Views. One presents the model as an item in a ListBox, the other presents it as a tab in a TabControl. The TabControl is to display tabs for the items that are selected in the ListBox, so that the tabs come and go as the selection changes.
I can easily synchronise the two controls by adding an IsSelected property to the Model and binding the ViewModels to it (a bit like this), but this will clutter the Model with presentation details that don't really belong there.
It seems like I need something between the Model and ViewModels to hold this extra state. Are there any patterns or examples of a good way to do this?
Use a ViewModel.
You've got a View that contains the two controls. Have a view model that will contain a list of ViewModels for the ListBox control to bind to. Also within this view model bind the listbox selection to a second list of viewmodels that the TabControl then also binds to.
That way your listbox drives what the tab control shows without this information entering the model which should stay oblivious to the existence of the view.
TabControl is ItemsControl, so you shouldn't be shy to bind its ItemsSource to ListBox.SelectedITems.
Obviously ViewModel for List should have a property that would produce ViewModel for Tabs:
public TabViewModel ItemTabModel { get { ... } }
And because TabControl is a bit funny, you'd need to add ItemContainerStyle to populate Content for TabControlItem, because the normal ItemTemplate for TableControl only affects headers for tabs.